Intersomatic cage

ABSTRACT

The invention relates to an intersomatic cage comprising a body ( 3 ) and a part ( 2 ) that is designed to dilate the intersomatic space between two vertebrae ( 8, 8 ′) by rotating the cage so that the cage ( 1 ) can be inserted into the space. The body ( 3 ) has a prism shape with a substantially planar upper surface ( 6 ) which can bear against the superior vertebral endplate ( 8 ) and a substantially planar lower surface ( 6 ′) which can bear against the inferior vertebral endplate ( 8 ′).

The present invention relates to the medical field and more particularlyto an intersomatic cage notably with an insertion tongue.

TECHNICAL FIELD

Certain pathologies of the spinal column, notably degenerative diseasesof the disk and of the facets and vertebral dislocations, compromise thesupporting capacity of the column and the distribution of load.

The treatments for these pathologies in their advanced stages make useof various stabilization systems by intradiscal implants of theintersomatic cage type, which may or may not be coupled to extradiscalimplants which notably combine the use of vertebral screws and plates orrods.

These intradiscal implant systems have made it possible to verysignificantly improve the treatment of the pathologies of the spinalcolumn by reestablishing the intervertebral space, which decompressesthe nerve roots and accelerates the bony fusion of the adjacentvertebrae.

These intersomatic cages are of several types: the first categoryincludes the threaded cages which are of essentially cylindrical shapeand which are screwed into the intervertebral space. WO 03/009786describes for example a cage of this type comprising an insertion tongueof rectangular, elliptical or oval shape situated at the front of thecage. The cross section of this tongue progressively increases along thelongitudinal axis of the cage from its end to the threaded part of saidcage, so as to allow the insertion of the latter into the intersomaticspace and then the expansion of this space by the screwing of the cage.

The main drawback of these types of threaded cages lies in the fact thatthey do not make it possible to reproduce a lordosis angle close to thenatural angle of the segment.

Impaction cages form the second category, in which the cage of mainlyparallelepipedal shape is inserted between the vertebrae by theapplication of impacts. The drawback of these cages is the difficulty ofinserting into the intersomatic space, by posterior approach, afterpartial laminectomies and facectomies, or else by transforaminal orlateral approaches, cages comprising a cross section of considerableheight in order to treat the vertebral segments where the naturalsagittal position is substantially lordotic, notably when the naturalangle to be reestablished is greater than 10°. Systems of cages that canbe expanded in situ have been developed to make it possible to obtainsuch heights in the anterior part of the cages, but often at the priceof diminished solidity, strength and stability.

The object of the present invention is therefore to propose anintersomatic cage in a single homogeneous body the geometry of which hasthe merit of remedying these drawbacks.

Another object of the present invention is to propose a device forinserting the intersomatic cage into the intervertebral space.

According to the invention, this object is achieved by virtue of anintersomatic cage comprising a body and a part designed to expand theintersomatic space between two vertebrae by rotating the cage in orderto be able to insert said cage therein by the effect of a push. The bodyhas a shape of a prism comprising an essentially flat superior surfacesuitable for pressing against the plate of the superior vertebra and anessentially flat inferior surface suitable for pressing against theplate of the inferior vertebra.

The advantage of the present invention lies in the fact that it allowsthe insertion of cages comprising a cross section of considerable heightand of which the superior and inferior faces are inclined, notablytoward the rear of the cage in order to offer a lordosis angle close tothe natural angle of the segment which may be substantially greater than10°, which is not possible for threaded cages inserted by posteriorapproach as described in WO03/009896.

Moreover, compared with the prior art, the invention also makes itpossible to insert a cage in parallelepipedal shape or of a trapezoidalcross section into the intervertebral space without necessarily havingto use impaction to insert the body of the cage, a pressure sufficientfor its insertion.

The features of the invention will appear more clearly on reading adescription of several embodiments given only as examples that are in noway limiting, with reference to the schematic figures in which:

FIG. 1 represents a front view in perspective of a cage comprising aninsertion tongue oriented on a plane inclined at approximately 45°relative to the horizontal plane of the cage according to a firstembodiment;

FIG. 1a represents a front view of FIG. 1 when the tongue is insertedinto the slightly expanded intersomatic space;

FIG. 1b represents a front view of FIG. 1 after rotation of the cagethrough approximately 45° and full expansion of the intersomatic space;

FIG. 2 represents a front view in perspective of a cage with lateralasymmetry for a unilateral, transforaminal or lateral approaches, withcentral insertion tongue in an oblique plane parallel to the superiorsurface of the cage according to a second embodiment;

FIG. 2a represents a front view of a cage with lateral asymmetryaccording to one variant embodiment with the insertion tongue insertedinto the slightly expanded intersomatic space;

FIG. 2b represents a front view of the cage according to this variantafter rotation of said cage through an angle of less than 45°;

FIG. 3 represents a view in perspective of a cage comprising twoinsertion rods according to a third embodiment;

FIG. 4 represents a view in perspective of a cage with lateral asymmetryfor transforaminal or lateral approaches with two insertion rodsaccording to a fourth embodiment;

FIG. 5 represents a view in perspective of a cage with an insertiontongue the lateral flanks of which are situated beyond the lateral sidesof the cage body according to a fifth embodiment;

FIG. 5a represents a front view of FIG. 5 when the insertion tongue isinserted into the slightly expanded intersomatic space;

FIG. 5b represents a front view of FIG. 5 after rotation of the cagethrough an angle β;

FIG. 6 represents a side view of two adjacent vertebrae and of a cagewith lateral asymmetry adapted for transforaminal or lateral approachesaccording to a sixth embodiment;

FIG. 7 represents a view in perspective of a cage with two flapsaccording to a seventh embodiment;

FIG. 7a represents a view in perspective of a cage with two bent rodsaccording to one variant embodiment;

FIG. 8 represents a front view in perspective of a cage comprising aninsertion tongue in an oblique plane and lateral wings on a part of thebody of the cage according to a ninth embodiment;

FIG. 8a represents a view similar to FIG. 8 but with curved wingsaccording to a first variant embodiment;

FIG. 8b represents a view in perspective of a cage with two oppositeflaps protruding from the lateral sides of the body and extending alongsaid sides according to a second variant embodiment;

FIG. 9a represents a front view in perspective of a cage the end ofwhich comprises two surfaces having a slope of helical gradientaccording to a 9th embodiment;

FIG. 9b represents a front view of FIG. 9a when the cage is in its finalposition with, in faint line, the position of the cage at the moment ofengagement of its end in the intersomatic space;

FIG. 9c represents a front view of a cage according to a firstembodiment, when the cage is in its final position with, in faint line,the position of the cage at the moment of engagement of its end in theintersomatic space;

FIG. 9d represents a front view of a cage according to a second variantembodiment, when the cage is in its final position with, in faint line,the position of the cage at the moment of engagement of its end in theintersomatic space;

FIG. 10a represents a right front view in perspective of a hybrid cageaccording to a 10th embodiment;

FIG. 10b represents the same cage as in FIG. 10a but in left frontperspective;

FIG. 10c represents a front view of FIG. 10 a;

FIG. 11a represents a view in perspective of an intersomatic cage withtwo removable insertion rods according to an 11th embodiment;

FIG. 11b represents a view in perspective of an intersomatic cageaccording to a first embodiment;

FIG. 11c represents a view in perspective of a hybrid intersomatic cageaccording to a second variant embodiment;

FIG. 12 represents a view in perspective of a cage with strips formingan integral part of an ancillary placement element according to a 12thembodiment;

FIG. 12a represents a top view of the cage and of the ancillaryplacement element in a first position;

FIG. 12b represents a top view of a similar cage and of a similarancillary placement element in a second position;

FIGS. 12c and 12d represent a top view of a cage of arched shapeaccording to a variant embodiment in two successive positions;

FIG. 13 represents a view in perspective of a cage according to a 13thembodiment;

FIG. 14 represents a view in perspective of a cage with flaps accordingto a 14th embodiment;

FIGS. 14a and 14b represent a front view of the cage with removableflaps in a retracted and deployed position;

FIG. 14c represents a detailed view in perspective of FIG. 14 a.

EMBODIMENT OF THE INVENTION

In the following description of the various intersomatic cages,reference is made notably to the horizontal plane of the cage that willbe assumed to be in a plane parallel to the axial or transverse plane ofthe human body, this horizontal plane corresponding to the position ofthe cage in its length when the latter is in its final position betweentwo vertebrae.

According to the first embodiment of the invention, FIG. 1 illustratesan intersomatic cage for posterior/postero-lateral approaches. This cagecomprises a body 3 with a conventional shape of an impaction cage,namely essentially parallelepipedal or a body 3 having a longitudinalsection of trapezoidal shape. This body 3 has a superior and inferiorsurface 6, 6′ designed to come into contact with the respective superiorand inferior vertebral plates. These two surfaces 6, 6′ are inclinedrelative to a horizontal plane so as to obtain a body 3 in which theheight of the anterior side 7 is greater than the height of theposterior side (not visible). These two surfaces 6, 6′ have between theman angle 5 ranging typically from 4° to 15°, or even greater, to allowthe vertebrae of the segment to be placed in lordosis. These surfaces 6,6′ may be covered with crenellations to prevent the cage from migratingforward or rearward. Moreover, the body of the cage may comprise athrough recess in the height direction so as to allow the stuffing ofgrafts promoting the bony fusion between the two adjacent vertebrae.

This cage also comprises a part 2 designed to expand the intersomaticspace between two vertebrae for the insertion of the intersomatic cage.The part 2, which in this instance will more commonly be called theinsertion tongue, has a substantially oblong shape with a height H′ andwidth W. This part 2 is arranged perpendicularly on the anterior side 7of the cage body 3 and in an inclined plane forming an angle ofapproximately 45° with the horizontal plane of the cage so that saidpart 2 extends in the direction of its height H′ along the diagonal ofthe anterior side 7 of the cage body 3.

It goes without saying that the incline of the tongue 2 may vary on anoblique plane comprising an angle of preferably between 40° and 60°relative to the horizontal plane of the cage. According to FIG. 1, theheight H′ of the tongue 2 is greater than the height of the highestsection H of the body 3. According to FIGS. 1a and 1b , it is noted thatthe dimensions of the tongue 2 make it possible to significantly reducethe angle of rotation necessary to expand the intersomatic space betweenthe vertebrae 8, 8′ in order to insert the whole of the cage body 3.Specifically, according to FIG. 1b , the intersomatic space of height H″which is greater than the height H of the body 3 in its anterior part isobtained by a rotation through an angle β close to 45°. This makes itpossible to significantly reduce the shearing stress forces F, F′exerted between them by the two vertebrae 8, 8′ of the segment. Theangle of rotation may also be greater than that necessary to obtain theheight H″, notably in order to ensure that cages comprising surfaceswith high crenellations pass. The lateral flanks of the tongue 2 make itpossible to insert and guide the body 3 pressing against the tworespective vertebral plates 8, 8′ along a plane inclined at the angle βin the intersomatic space before said body 3 reaches its final positionand performs a slight contra-rotation under the effect of thecompression of the vertebrae 8, 8′.

For the insertion of the cage, an instrument may be screwed on theposterior side of the body 3. After the extraction of all or some of theintervertebral disk, and if necessary after application of dilationcandles in the intersomatic space, then moving the nerve roots aside,the cage is implanted in five steps, namely: insertion of the cage intothe rachidian canal; rotation; insertion/pressing of the insertiontongue 2 into the intervertebral space; contra-rotation; pushing thecage into the intervertebral space. More precisely, the implantationsteps are as follows:

insertion of the cage into the rachidian canal with its insertion tongue2 in the vertical position. When the front of the insertion tongue 2makes contact with the vertebrae, the cage is turned through an anglesubstantially less than 90° in order to tilt the insertion tongue 2 tothe horizontal which allows it to be inserted into the slightly expandedintervertebral space. The cage is then again turned through an angle ofless than 90°, but in the opposite direction to the second step, whichhas the effect of expanding the intervertebral space to a height closeto the height H′ of the insertion tongue 2 of the cage. The latter isthen pushed or, if necessary, impacted, into the intervertebral space toits final position. The insertion tongue can be made of a differentmaterial from that of the body, for example resorbable material designedto disappear in order to leave room for the bony growth, or anosteoconductive material designed to promote said bony growth.

FIG. 2, according to the second embodiment of the invention, representsan intersomatic cage for unilateral, transforaminal or lateralapproaches, that is to say a cage which is inserted in a posterolateralor lateral manner, and of which the final positioning is situated in theanterior part of the intersomatic space, perpendicular to the sagittalplane. The instrumentation of an intervertebral segment with such a cagedoes not in principle require the insertion of a second cage. Theparticular feature of this cage lies in the fact that it comprises acage body 3 which is asymmetrical not lengthwise (as described in thefirst embodiment) but widthwise. The lordosis angle 5′ that is soughtfor the final position of the vertebrae of the segment is given, in thiscase, by the angle obtained by the extension of the superior andinferior surfaces 6, 6′ widthwise. According to FIG. 2, the cagecomprises an insertion tongue 2 which is in a plane P parallel to aplane P′ containing the superior surface 6 of the cage body 3. Thetongue 2 is off-center in a plane parallel to a horizontal plane halfwayup the cage body 3.

In a variant shown by FIGS. 2a and 2b , the tongue 2 is in an obliqueplane relative to the plane containing the superior or inferior surfaceof the body 3. This makes it possible to lengthen the height H′ of theinsertion tongue 2 which, in its turn, reduces the angle of rotation βnecessary for the sufficient expansion of the intersomatic space H″ inorder to ensure that the body 3 of the cage passes. This angleaccordingly reduces the shearing stress forces exerted between thevertebrae 8, 8′ of the segment, which may promote the maintenance of thetrajectories of the implant into the intersomatic space.

When the insertion tongue 2 first makes contact against the vertebrae 8,8′ (FIG. 2a ), the tongue is, if necessary, inserted directly withoutprior rotation into the preexpanded intersomatic space or, if necessary,after a slight rotation impressed upon the cage in order to align thetongue 2 in the plane of the intersomatic space. After the tongue 2 hasbeen fully inserted, a rotation through approximately 45° is carried out(FIG. 2b ) which has the effect of expanding the space by a height H″that is sufficient to ensure that the body 3 with its highest crosssection passes between the superior and inferior faces 6, 6′. The cageis then pushed or, if necessary, impacted, until the body 3 fully entersthe intersomatic space and is pushed into its final position, in theanterior part of said space. Although according to FIG. 2b the angle ofrotation β is approximately 45°, it may be smaller or greater dependingon the ratio between the height and the width of the cage (for examplebetween 30° and 60°). This cage may also be arched relative to itslongitudinal axis in order to conform to the shape of the anatomy of thevertebral body in its anterior part.

According to a third embodiment of the invention, FIG. 3 represents anintersomatic cage which comprises a cage body 3 with a geometric shapesimilar to the cage body of the first two embodiments. Two rods 13, 13′are mounted on the anterior side 7 of the body 3 in two diagonallyopposite corners. These two rods 13, 13′ are oriented on an axisperpendicular to the anterior side 7 and have sufficient length to beable to be inserted far enough forward between two adjacent vertebraeand serve as lever arms for expanding the space by a rotary movement.Preferably, this length is between 6 and 7 mm. The arrangement of theserods 13, 13′ makes it possible to obtain a technical effect similar tothat obtained by the insertion tongue 2 according to the firstembodiment when the cage is inserted into the intervertebral space.

This cage is inserted through the rachidian canal on a horizontal planeof the body 3, or else, if it is desired that the rods 13, 13′ return toa vertical plane (for example in order to bypass the nerve roots) thebody must be tilted in a plane between 40° and 60° depending on theheight-width ratio of the anterior side 7 of the cage body 3. When therods 13, 13′ touch one or both vertebrae of a segment, the cage is thentilted until the rods 13, 13′ are again in a horizontal plane (the bodyof the cage then being in an oblique plane between 40° and 60° dependingon the height-width ratio of the anterior side 7 of the body).

According to a variant, the two rods can be arranged relative to oneanother so as to return to a vertical plane, horizontal plane or else toan oblique plane forming an angle different from 45° with the horizontalplane of the cage. The plane will be chosen depending on the desire tolimit or increase the angle of rotation and the force necessary for thesufficient expansion of the intersomatic space for the insertion of thebody 3. The plane may pass over the longitudinal median axis of the bodyof the cage or be situated beside said axis, in order to increase orattenuate the cam effect of the body at the time of its rotation, of oneor other of its sides. One or more median rods between the two rods maybe added. The cross section of the rods may naturally be of any shape,notably square, oval or oblong.

According to a fourth embodiment of the invention, FIG. 4 represents acage which differs from the cage according to the previous embodiment inthe geometric shape of the body 3 which is suitable for transforaminalor lateral approaches, that is to say that it is a cage designed to bepositioned laterally in the intersomatic space. The body 3 of this cagehas a geometric shape similar to that of the second embodiment (FIG. 2)and therefore has a lateral side 3″ that is higher than the other (3′),while its anterior side 7 and posterior side (not visible) are ofsimilar height. The rods 13, 13′ are mounted on the anterior side 7 ofthe cage body 3. These rods 13, 13′ may form an integral part of thebody, or they may be fitted, crimped or screwed into said body by one oftheir ends. These rods may be made of a material different from that ofthe body, for example a resorbable material designed to disappear inorder to leave room for the bony growth, or an osteoconductive materialdesigned to promote said bony growth.

According to a fifth embodiment, FIG. 5 represents an intersomatic cagefor posterior/posterolateral approaches which comprise, on the one hand,a cage body with a geometric shape preferably identical or similar tothe cage body according to the first embodiment and, on the other hand,a part 2 designed to expand the intersomatic space. This part 2, whichwill also be called the insertion tongue, is arranged on the anteriorside 7 of the body 3 of the cage. This tongue 2 extends beyond thelateral sides of this body 3′, 3″, so that the height H^(bis) of thetongue 2 is greater than the diagonal of the anterior side 7. Theincreased dimensions of this tongue 2 make it possible to reduce theangle of rotation necessary for the expansion of the intersomatic space.In other words, this tongue 2 reduces the necessary torsional force andthe cam effect of the body. The lateral edges of the tongue 2 are notnecessarily parallel but preferably they do not protrude relative to thesuperior and inferior faces 6, 6′ of the cage body 3 once the cage is inits final position so as not to interfere with the contact of said faceswith their respective vertebral plate.

FIG. 5a represents the intersomatic cage just before a rotation isimpressed on the body 3 when the insertion tongue 2 is horizontal in theintersomatic space between the vertebrae 8, 8′. FIG. 5b illustrates theend of the rotation of the cage through an angle β, with theintersomatic space expanded to a height H″ sufficient to be able to pushthe whole of the body 3 of the cage into the intersomatic space withoutthe surfaces 6, 6′ rubbing the vertebral plates 8, 8′. Specifically, theheight H of the cage with its highest cross section is much smaller thanthe height H″ of the intervertebral space necessary for the body 3 topass. This height difference makes it possible to reduce as much aspossible the angle β, and consequently the effect of the shearing stressforces F, F′, the distraction force necessary for the expansion, and thecam effect of the body at the time of the rotation. FIG. 5b shows thatthe expansion of the intervertebral space has been obtained by arotation through an angle β close to 45°, while the height of the body 3is significantly greater than its width. This figure also shows that itis possible to apply profiles of considerable crenellations on thesurfaces 6, 6′ without the latter hampering the insertion of the cage.

According to a sixth embodiment, FIG. 6 represents a cage, forunilateral, transforaminal or lateral approaches, said cage being in itsfinal position between two vertebrae 8, 8′. This cage comprises aninsertion tongue 2 arranged on the anterior side 7 of a cage body 3 witha geometric shape similar to the cage body of the second embodiment. Theparticular feature of this cage lies in the fact that, unlike the secondembodiment, the tongue 2 extends beyond the lateral sides of the body 3so as to obtain the advantages described in the fifth embodiment not fora posterior/posterolateral approach but for unilateral, transforaminaland lateral approaches.

According to a seventh embodiment, FIG. 7 represents an intersomaticcage for posterior/posterolateral approaches comprising a cage body 3with a geometric shape that is preferably identical or similar to thecage body according to the first embodiment and two flaps 19, 19′ oftrapezoidal cross section placed on the anterior side 7 of the body 3and oriented in a plane corresponding to that of the insertion tongueaccording to the previous embodiment. The flaps 19, 19′ are respectivelyarranged close to a first and second corner of the anterior side 7 saidcorners being diagonally opposite. These flaps 19, 19′ comprise lateralflanks 20, 20′ protruding beyond the edges of the anterior side 7 of thecage body 3. A variant as illustrated by FIG. 7a consists insubstituting for the flaps two rods 13, 13′ comprising a first segmentthat is oblique relative to the longitudinal axis of the body 3, and asecond rectilinear segment oriented on another axis in order that a partof the rods 13, 13′ are situated outside the vertical plane coincidingwith the two lateral sides of the body 3.

According to an eighth embodiment, FIG. 8 illustrates an intersomaticcage similar to the cage described in the fifth embodiment except thatthis cage also comprises, in the extension of the tongue 2, a wing 9, 9′arranged along each of the two lateral sides 3′, 3″ of the cage body 3.The height H^(bis) of the tongue 2 is substantially greater than theheight of the body 3 at its highest section, namely at its anterior side7. It goes without saying that the shape of the wings 9, 9′ and theirdimensions can be arbitrary. For example, the width of the wings 9, 9′may increase or decrease along the longitudinal axis of the cage and/orextend over the whole length of the lateral sides 3′, 3″ of the body 3.The wings may also be noncontinuous and therefore consist of severalsegments along the lateral sides.

Another example is illustrated by FIG. 8a which represents a cagecomprising curved wings 9, 9′ so as to promote the changes of trajectoryin the intersomatic space and thus improve the final positioning of saidcage. According to a variant not shown, these wings 9, 9′ may alsodisplay a rectilinear shape inclined at any angle along the lateralsides, an angle that differs from the plane formed by the tongue 2.

According to another example as shown by FIG. 8b , the cage comprises aninsertion tongue combining certain features of the intersomatic cagesillustrated in FIGS. 7 and 8 a.

According to a ninth embodiment of the invention, FIG. 9a represents anintersomatic cage for posterior/posterolateral approach comprising abody 3 and a part 2 ^(bis) designed to expand the intersomatic spacebetween two vertebrae for the insertion of the cage. The superior andinferior faces 6, 6′ of the body 3 are not parallel but positioned at anangle 5. This angle varies depending on the cages and is suitable forthe lordotic angle desired depending on the vertebral segment that isinstrumented. This angle may range typically from 4° to 15°, and evengreater. The body may also have parallel superior and inferior surfaces.The part 2 ^(bis) is in the extension of the body 3 and comprises on theone hand a superior and inferior face 10, 10′ (FIG. 9b ) designed tocome into contact with the respectively superior and inferior vertebraof the intersomatic space and on the other hand two lateral faces 11,11′. These faces 10, 10′, 11 and 11′ converge from the respective edgesof the anterior side of the body 3 up to a flat face 2 n centeredhalfway up and halfway across said anterior side. This central face 2 nhas a shape similar to an insertion tongue as described in certain ofthe previous embodiments but with much smaller dimensions than thedimensions of the cage body 3. This flat face 2 n stretches in thedirection of the diagonal of the anterior side so as to form an angle βwith the horizontal plane of the cage 3. The faces 10, 10′ are identicaland are inclined and curved so as to reproduce the beginning of a slopewith a helical gradient in order to be able to transmit a rotation ofthe body 3 simply by pressing on the posterior part of said body 3 whenthe central part 2 n is arranged in the intersomatic space.

According to FIG. 9b , the cage illustrated in faint line represents thelatter when the flat surface 2 n is arranged in correspondence with theintersomatic space just before the insertion of the end of the part 2^(bis) into the intersomatic space. At this moment, the cage body 3 isinclined by approximately 45° relative to the vertebral plates and thesurfaces 10, 10′ are in contact with the latter. When a pressure isexerted at the back of the body 3, the latter begins to rotate by virtueof the profiles of the surfaces 10, 10′ until it is again in thehorizontal plane of the cage.

According to a first variant embodiment, FIG. 9c illustrates a cagesimilar to that represented in FIGS. 9a and 9b but in which the part 2^(bis) extends along a longitudinal axis that is off-center from themedian longitudinal axis of the body 3 so that the surface 2 n stretchesalong a vertical axis. FIG. 9c represents in heavy lines the finalposition of the cage and in faint line its position of engagement of thecage 3. The insertion of the end of the part 2 ^(bis) into theintersomatic space will in this instance cause an autorotationalmovement of the order of 90°.

According to a second variant embodiment, FIG. 9d represents a cage inwhich the part 2 ^(bis) extends in a longitudinal axis that isoff-center from the median longitudinal axis of the body so that thesurface 2 n stretches along an axis inclined at an angle β correspondingto 45°. The insertion of the end of the part 2 ^(bis) will in thisinstance cause an autorotational movement of the order of 45° but with amore pronounced cam effect on one side of the body 3 than the other.

Moreover, it goes without saying that the part 2 ^(bis) may be situatednot on the anterior side but on one of the lateral sides of the cagebody for transforaminal or lateral approaches.

FIGS. 10a to 10c represent an intersomatic cage according to a 10thembodiment of the invention. This cage combines certain features of theprevious embodiment with, in particular, the first embodiment. Moreprecisely, the cage comprises on the one hand an insertion tongue 2 ofdepth Dp requiring an intentional rotational movement of the surgeon,and on the other hand an intermediate part of depth Dp′ and arrangedbetween the insertion tongue 2 and the anterior side of the cage body 3.This intermediate part comprises two lateral surfaces 11, 11′ that areprofiled so as to orient the tongue 2 into an inclined position relativeto the horizontal plane of the cage at an angle β(FIG. 11c ). Moreover,the superior and inferior surfaces 10, 10′ (FIG. 11b ) of saidintermediate part are inclined and curved so as to reproduce thebeginning of a slope with a helical gradient. The advantage of this cageis that it obtains a partial expansion of the intersomatic space througha slight rotation in order to be able subsequently to push the cage andcause the autorotational effect by virtue of the intermediate part witha much weaker pressure than the pressure that would have to be appliedto a cage similar to that illustrated in FIG. 9a . This combination alsohas the advantage over a cage as described in the first embodiment,because of the presence of a twisting component, of requiring no morethan a small angle of rotation which reduces the shearing stress forcesbetween the two adjacent vertebrae. Specifically, when these forces aretoo strong, they are likely to cause the cage to “slip sideways” at themoment of the final push and thus cause it to come out of the desiredtrajectory. Finally, the height of the insertion tongue 2 may be lessthan the height H of the cage body 3 which may be an advantage to avoidthe hard or soft tissues at the moment of insertion through therachidian canal.

In order to insert this cage, the insertion tongue 2 is oriented incorrespondence with the intersomatic space and is then inserted betweenthe vertebral plates. A rotation of substantially less than 90° isimpressed by the surgeon in order to partly expand the intersomaticspace and then, before this space is as high as the height of the body3, the cage is pushed forward, and the intermediate part takes over andcontinues the expansion of the intersomatic space according to theautorotational principle, without any other intentional rotation beingnecessary on the part of the surgeon. In a variant (not shown), the partdesigned to expand the intersomatic space is situated on one of thelateral sides of a cage body with lateral asymmetry for transforaminalor lateral approaches.

Another variant (not shown) consists in combining the features of theanterior part of a cage with slopes with a helical gradient of the ninthembodiment, with, for example, the lateral wings of the eighthembodiment. This hybrid cage operates in the reverse manner to thehybrid cage of the 10th embodiment in that the cage is initiallyinserted by pushing or impaction into the intersomatic space via itspart with slopes of helical gradient, which initiates an autorotationmovement and slightly expands the intervertebral space, then, once thewings are engaged in the intersomatic space to a sufficient depth, thesurgeon exerts an intentional rotation to complete the expansion to asufficient height to cause the body of the cage to enter fully simply bypushing. A variant embodiment consists in replacing the anterior partwith slopes of a helical gradient with an anterior face of the bodyhaving a round or ogival profile helping the initial push or impaction.

According to an 11th embodiment as illustrated by FIG. 11a , theexpansion of the intersomatic space between two vertebrae is achieved bytwo rods 13, 13′ forming an integral part of an ancillary placementelement of the cage. The advantage of this embodiment over the thirdembodiment is that it makes it possible to eliminate the spacerequirement formed by the rods in the intersomatic space. Twolongitudinal runners 15, 15′, designed to receive the rods 13, 13′, passthrough the cage body 3 from end to end. More precisely, these runners15, 15′ are arranged along two distinct longitudinal axes perpendicularto the anterior side 7 of said body 3 and situated in two diagonallyopposite corners of said side 7. The rods may also be oriented in anaxis not parallel to one of the lateral sides of the body. In order toensure the stability of these rods 13, 13′, they may be attached to thebody 3 in a temporary manner, for example at the height of the posteriorpart of said body 3 or by an attachment (by screwing or other fasteningmeans) to the ancillary placement element (not shown) of the cage. Therods 13, 13′ may already be in position as shown in FIG. 11a or may beslid, after the insertion of the cage and its passage into the rachidiancanal. The rods 13, 13′ can be withdrawn after the rotation of the cagebody 3 and before it is pushed into the intersomatic space, or elseafter said push, when the cage is in its final position. FIG. 11brepresents a variant in which only one of the rods 13, 13′ is removable,the other forming an integral part of the cage body 3. This variant maybe advantageous for reducing the space requirement of the intersomaticspace to only a single rod, while providing stability to the lever armformed by the two rods 13, 13′.

FIG. 11c introduces a second variant in which the cage comprises a cagebody 3 and a part 11 arranged on the anterior side of the body 3. Thispart 11 has a superior surface 10 and inferior surface (not visible)which are inclined so as to reproduce the beginning of a slope with ahelical gradient. This cage makes it possible to obtain an effectcomparable to that obtained by the cage according to the 10th embodimentwhen it is inserted into the intersomatic space, namely a partialexpansion of this space by a slight rotation of the ancillary placementelement (not illustrated) in order to be able subsequently to push thecage and cause the autorotational effect by virtue of the profile of thesuperior and inferior surfaces of the part 11. This cage in thisinstance incorporates two moveable rods 13, 13′ arranged in a horizontalplane parallel with a mid-plane of the cage body 3. One of the rods (13)is arranged in a longitudinal runner 15 so that its end protrudes in theextension of the part 11 which comprises a truncated end 2 while theother rod 13′ is arranged in a runner or a longitudinal groove 16. Afterthe rods 13, 13′ are inserted into the intervertebral space, a rotarymovement is impressed on the ancillary placement element so as to raisethe rod 13. This movement may be slight (less than 45°) because itsimply has to allow the engagement of the truncated end 2 of the part 11in the half-expanded intervertebral space (the body 3 also being in thesame plane as the two rods 13, 13′, namely less than 45°), before a pushor an impact on the posterior part of the body 3 causes the additionalrotation necessary for the expansion of the intersomatic space, to asufficient height for the insertion of the body into said intervertebralspace. The advantage of this variant is that, because of the small angleof rotation necessary for the lever effect, this reduces the cam effectinduced by the rotation, which can be advantageous in the presence ofnerves or hard tissues nearby. It is quite clear that the profile of thepart 11, and mainly the superior surface 10 and inferior surface (notvisible) can vary so as to provide the most ergonomic link to thesuperior face and/or inferior face of the body 3. Naturally, theinsertion tongue 2 part with its depth Dp may be not only in a planethat is oblique relative to the horizontal plane along the horizontalplane of the cage, at an arbitrary angle, but may also be in ahorizontal plane, namely indistinguishable from or parallel to thesuperior or inferior surfaces of the cage body.

According to a 12th embodiment, FIG. 12 represents a conventional cageconsisting only of a body 3. This body 3 has, on each of its lateralsides, a groove 16, 16′ oriented in the direction of the longitudinalaxis of the cage. These grooves 16, 16′ are designed to receive strips21, 21′ forming an integral part of an ancillary placement element,these strips having the function of expanding the intersomatic spacebetween two vertebrae, according to the same principle as that describedfor the embodiment. In order to hold the strips inside the grooves, thelatter preferably have a cross section of trapezoidal shape. Naturally,the strips may have a different section, notably oval or oblong, if theycan be held inside their grooves 16, 16′ by a mechanical means, forexample at the ancillary placement element or by a member for connectionbetween the strips at their anterior end protruding from the body 3.Note that the strips may be arranged not on the lateral sides of thebody but on its superior and inferior surfaces, or even a configurationin which one strip has its groove in the superior surface or inferiorsurface of the body and the other strip has its groove in one of thelateral sides. Moreover, one of the strips may have a greater width thanthe other.

A variant embodiment (not shown) consists in combining a removable stripfeature of this 12th embodiment with a wing feature of the ninthembodiment.

According to FIG. 13a , the strips 21, 21′ are mounted on the body 3 atthe time of insertion of the cage. The ancillary placement elementcomprises notably a piece 22, for example of rectangular shape, suitablefor being fitted into, or otherwise secured to, the posterior part ofthe body 3. This piece 22 clamps the strips 21, 21′ and helps to keepthem in the grooves 16, 16′. It also helps to transmit the rotationalforce applied to the handle 221 of the ancillary. The cage body 3comprises, on its posterior side, a screw pitch 223 in order to be ableto screw an instrument 222 into it. This instrument 222 slides insidethe piece 22 and makes it possible to push the body 3 after the rotationof the latter has been achieved. In a variant embodiment (not shown),the body 3 is not pushed individually, but it is the strips 21, 21′ thatare withdrawn once the body 3 is in its desired position. Naturally, anyother placement system associating strips 21, 21′ with a body 3 can beused for the purposes of expansion and insertion of the body 3.

The strips 21, 21′ can also be positioned in an intermediate position(FIG. 12b ), or even on the periphery of the posterior face of the body3, notably if it is desired to reduce the width of the cage at themoment of its passage into the rachidian canal. The depth of the grooves16, 16′ is not necessarily constant and may decrease from the rear tothe front of the body 3 (FIG. 12b ). Similarly, it is possible for thestrips 21, 21′ not to be aligned in two parallel axes (FIG. 12b ),and/or to have a nonconstant, or increasing or decreasing width.

FIGS. 12c and 12d represent a variant of a cage comprising an archedbody so as to better conform to the shape of the contour of thevertebral bodies, whether it be for a posterior or transforaminal orlateral approach. Once the cage body 3 is close to its final position,the strip 21 that is on the concave side of the body 3 is withdrawn andpressure is applied to said body 3 via the instrument 222 in an axisthat is oblique relative to the longitudinal axis so as to be able tomake it pivot on an axial or sagittal plane (on the assumption that thestrips are in a position of distraction of the intersomatic space).

FIG. 13 represents a 13th embodiment combining the features of theinsertion flaps of the ninth embodiment with the retractable strips ofthe 12th embodiment, namely in which the cage body 3 comprises on eachof these lateral sides an arched longitudinal groove 16, 16′ into whichthe arched strips 21, 21′ that form an integral part of an ancillaryplacement element are inserted. There are multiple variant embodiments,because the strips can also be straight or in a plane that differs fromthe plane of the flaps and the strips can also be combined with aninsertion tongue of the fifth embodiment.

According to a 14th embodiment (FIG. 14), a first and a second removableflap 22, 22′ is attached on the end respectively of a first and secondrods 23, 23′ arranged in a first and second grooves 16, 16′, saidgrooves being situated along one and the other of the lateral sides,respectively in the superior part and inferior part of the body 3. Theflaps 22, 22′ may already be in place when the cage is inserted or maybe slid into the grooves 16, 16′ after the body 3 has been inserted inorder to achieve the rotation. The value of this cage is that it ispossible to retract these flaps 22, 22′ after exercising rotation of thecage. The profile of the cross section of each groove 15, 15′ preventsthe flaps 22, 22′ from rotating about their rod 23, 23′ when thevertebrae exert a force “F” and “F1” against said flaps.

A variant embodiment illustrated by FIGS. 14a, 14b and 14c consist ininserting the flaps 22, 22′ into ducts 24, 24′ passing through the bodylengthwise and comprising a cross section corresponding to that of theflaps. Two rotational enclosures 25, 25′ arranged on the anterior side 7of the body allow the flaps 22, 22′ to accomplish an arc of a circle upto the abutment 23 (FIG. 14c ) in order to be able to be deployed intheir protruding position in situ in order therein to fulfill theirlever-arm function. The cage is inserted with or without flaps throughthe rachidian canal. In contact with the anterior side 7 of the bodywith the vertebrae, the flaps 22, 22′ are pushed via their respectiverod 23, 23′ into the ducts 24, 24′ until they emerge in their respectiverotational enclosures 25, 25′. If the flaps are already in their ductswhen the cage is inserted, they simply have to be deployed. Thedeployment takes place via a rotation of the order of 190° of the rodswhich rotates the flaps 22, 22′ up to the abutment 23. The flaps arethen inserted into the intersomatic space and the body is rotated forthe purposes of expansion. The abutment resists the force “F” exerted bythe vertebra. In order to further stabilize the lever arm, the rods maybe directly attached to the body 3, for example in its posterior part,or conversely only to the insertion device of the body. As a variant,the flaps can be deployed immediately when the body is inserted throughthe rachidian canal, then, after the rotation of the body, the flaps arefolded back into their entrance position as shown in FIGS. 14a and 14b ,then retracted from the body along their duct. If the surface of thevertebra prevents such a reverse rotation of the flaps, the flaps can bepushed forward past the end of the abutment 23 and then complete therotation and be retracted from the body. Such a device can also combinea movable flap and a fixed flap, or a movable flap and a rod. A variantembodiment consists in furnishing the body with deployable thensemi-retractable flaps, that is to say that they are not retracted withthe placement device after the body is inserted, but are retractedinside the body in order to limit the space requirement of theintersomatic space.

It goes without saying that certain features of any embodiment can besubstituted and/or added to certain features of one of the otherembodiments. In particular, each of the features joined to the body ofthe cage, insertion tongue, flaps, insertion rods, wings, can be made ina resorbable material designed to disappear in order to leave room forthe bony growth, or an osteoconductive material designed to promote saidbony growth.

All the variants are also capable of being applied to cages which arenot designed to be inserted via a posterior approach, notably to cagesfor transforaminal or lateral approaches.

Moreover, the end of the part designed to expand the intervertebralspace has, in certain embodiments, a bevelled profile. Moreover, all thesharp edges of the body can be blunted. Convex or concave surfaces canalso be produced on the side of the body 3 containing the part designedto expand the intersomatic space in order to make the transition betweenthis part and said body 3 easier.

Finally, the subject of the present invention also relates to twomethods for inserting the cage into the intersomatic space. Moreparticularly, the invention relates to a first method for inserting thecage as described in certain of the preceding embodiments, said methodcomprising the following steps:

-   -   the cage is inserted into the rachidian canal with its insertion        tongue 2 vertical until the front of the insertion tongue 2 is        in contact with the vertebrae;    -   the cage is then turned a quarter turn or an angle substantially        less than 90° in order to tilt the insertion tongue 2 to the        horizontal which allows it to be inserted into the slightly        expanded intervertebral space;    -   the cage is then again turned a quarter turn or an angle        substantially less than 90°, but in the opposite direction to        the second step, which has the effect of expanding the        intervertebral space to a height close to the height H′ of the        insertion tongue 2 of the cage;    -   the latter is then pushed or, if necessary, impacted, into the        intervertebral space to its final position.

The invention also relates to a second method for inserting a cage asdescribed in other preceding embodiments, said method comprising thefollowing steps:

-   -   the cage is inserted into the rachidian canal until the front of        said cage is in contact with the vertebrae;    -   a pressure and/or impaction is applied to the cage causing an        autorotation movement of the latter allowing the expansion of        the intersomatic space;    -   an additional pressure is then applied to the cage in order to        insert it into the intersomatic space up to its final position.

The invention claimed is:
 1. A method for inserting an intersomatic cagein an intersomatic space between two vertebrae, the intersomatic cagecomprising a body of rectangular or trapezoidal cross-section that hasan essentially flat superior surface capable of resting against asuperior vertebra and an essentially flat inferior surface capable ofresting against an inferior vertebra and at least one part that extendsfrom said body and is configured for dilating the intersomatic space inresponse to rotation of the intersomatic cage after insertion of said atleast one part in the intersomatic space between the superior vertebraand the inferior vertebra, wherein the method comprises the successivesteps of: a) inserting said at least one part, but not said body fromwhich said at least one part extends, in the intersomatic space betweensaid superior and inferior vertebrae, b) then rotating the intersomaticcage in a given direction of rotation by an angle up to 90°, such thatthe intersomatic space is dilated by said at least one part to a spacingwhich is superior to the distance between the essentially flat superiorsurface and the essentially flat inferior surface of the body of theintersomatic cage, c) inserting the body of the intersomatic cage intothe thus-dilated intersomatic space by pushing the body of theintersomatic cage into the thus-dilated intersomatic space, and d)counter-rotating the intersomatic cage in a direction opposite to thedirection of rotation in step b), or allowing the intersomatic cage tocounter-rotate in a direction opposite to the direction of rotation instep b), until the essentially flat superior and inferior surfaces ofthe body of the intersomatic cage come to rest against the superior andinferior vertebra.
 2. The method according to claim 1, wherein in stepb), the intersomatic cage is rotated by an angle less than 90° in saidgiven direction of rotation.
 3. The method according to claim 2, whereinsaid at least one part is retractable into the body of the intersomaticcage or is fully removable from the body of the intersomatic cage and isretracted or removed after step d) of claim
 1. 4. The method accordingto claim 1, wherein in step d) the intersomatic cage is allowed tocounter-rotate in the direction opposite to the direction of rotation instep b) through compression of the intersomatic cage between thesuperior and inferior vertebrae, without applying an external rotationalforce to the intersomatic cage, until the essentially flat superior andinferior surfaces of the body of the intersomatic cage come to restagainst the superior and inferior vertebrae.
 5. The method according toclaim 1, wherein said at least one part is retractable into the body ofthe intersomatic cage or is fully removable from the body of theintersomatic cage and is retracted or removed after step d) of claim 1.6. The method according to claim 1, wherein one said part, or a planedefined by two said parts, is arranged in an inclined plane relative tothe essentially flat superior and inferior surfaces of the body of theintersomatic cage.
 7. The method according to claim 6, wherein the angleof said inclined plane is comprised between 40° and 60° relative to theessentially flat superior and inferior surfaces of the body of theintersomatic cage.
 8. The method according to claim 1, wherein theintersomatic cage is rotated in step b) by an angle between 40° and 60°.9. The method according to claim 1, wherein said at least one part ofthe intersomatic cage comprises a part having a distal end and aproximal end which is connected to a face of the body of theintersomatic cage, said part extending over a width from the proximalpart connected to the body to the distal part, said part having across-section in a sectional plane facing to said face of the body whichcross-section has a short dimension and a long dimension, theintersomatic cage comprising an inclined first plane defined by andextending along the entire long dimension of said part and extendingthrough the middle of the short dimension along the entire length of thelong dimension and extending across the width of said part, whichinclined first plane is arranged at an angle that is inclined up to 90°relative to the essentially flat superior and inferior surfaces of thebody of the intersomatic cage, said inclined first plane intersectingwith a second plane in extension of said essentially flat superiorsurface of the body at a first end of the long dimension of the part,said inclined first plane furthermore intersecting with a third plane inextension of said essentially flat inferior surface of the body at asecond end of the long dimension of said part.
 10. The method accordingto claim 9, wherein said inclined plane of the intersomatic cage isarranged at an angle that is inclined between 40° and 60° relative tothe essentially flat superior and inferior surfaces of the body of theintersomatic cage.
 11. The method according to claim 1, wherein the bodyof rectangular or trapezoidal cross-section of the intersomatic cage hasblunted edges.
 12. The method according to claim 1, wherein theintersomatic cage is rotated in step b) by an ancillary placementelement.